ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Influence of kaolin in enhancing AC response and humidity sensing properties of polythiophene/kaolin composites

Devindrappa Patil, M. Madeshkumar, M. Revanasiddappa, S. Manjunatha, M. Veerabhadrayya, and Y. T. Ravikiran

Department of Physics, School of Applied Sciences, REVA University, Bangalore, India

E-mail: ytrcta@gmail.com

Received: 10 November 2024  Accepted: 17 August 2025

Abstract:

In this study, polythiophene (PT) synthesized through in situ polymerization was combined with varying percentages of kaolin clay to prepare polythiophene/kaolin clay (PTKC) composites. The resulting composites were examined through Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). FTIR and XRD results indicated a significant interaction between kaolin clay and polythiophene within the composites. AC conductivity, dielectric constant, and loss tangent of the composites were examined at room temperature across a frequency range of 50–5 MHz. The AC conductivity of PTKC-2, PTKC-6, and PTKC-8 was observed to be marginally greater than that of pure polythiophene. The variations noted in the dielectric constant and loss tangent as a function of frequency can be elucidated through the concept of Maxwell–Wagner polarization. The loss tangent curves for PTKC-2, PTKC-6, PTKC-8, and PTKC-10 displayed peaks throughout the measured frequency range, a phenomenon that can be elucidated by the Rezlescu model. To evaluate the humidity sensing capabilities, resistance of both PT and PTKC composites was assessed at various relative humidity levels in the range of 11–95%. Among all the composites, the PTKC-4 composite demonstrated the highest sensitivity to humidity, a low detection limit, and excellent linearity, positioning it as a promising candidate for the advancement of humidity sensors.

Keywords: Polythiophene; Kaolin; Polymer composites; Electrical properties; Fourier transform infrared spectroscopy; X-ray diffraction (XRD); Humidity sensor

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04372-2

Chemical Papers 79 (12) 9089–9097 (2025)